Fog generation by an ultrasonic transducer operating in water is known in the art. A typical ultrasonic fog generator is shown in FIG. 1. An ultrasonic transducer 3 (or ultrasonic wave nebulizer or simply ultrasonic nebulizer, all the terms being used interchangeably throughout the specification and claims) typically includes an oscillator that causes oscillation of an immersed membrane in water in an enclosure 4. The membrane vibrates at very high frequencies, such as but not limited to, 1.7 MHz. The vibration breaks down the water into tiny vapor particles, such as 1-50 microns in diameter or more preferably 1-10 microns. A fan 5 is provided that blows air into enclosure 4 via an inlet port 6. The air blows over the water and carries the tiny vapor particles outwards as a fog mist through an exit port 7. The water vapor particles are so small that they mix with the surrounding air and leave no feel or trace of wetness.